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    Two DHCP in one physical network

    Scheduled Pinned Locked Moved DHCP and DNS
    18 Posts 4 Posters 16.3k Views
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    • Q
      qshiroe
      last edited by

      vlan great idea, be work if clients work with a common network switch?

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      • johnpozJ
        johnpoz LAYER 8 Global Moderator
        last edited by

        huh??  be work if clients what?

        Its not a idea dude - its how its done.  Running multiple layer 3 networks on the same layer 2 is just borked plain and simple..

        An intelligent man is sometimes forced to be drunk to spend time with his fools
        If you get confused: Listen to the Music Play
        Please don't Chat/PM me for help, unless mod related
        SG-4860 24.11 | Lab VMs 2.8, 24.11

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        • Q
          qshiroe
          last edited by

          In general, the only way to make it work, divide the network into 2 parts

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          • johnpozJ
            johnpoz LAYER 8 Global Moderator
            last edited by

            That is how it should done yes, you DO NOT RUN multiple layer 3 networks on the same layer 2 wire.. It is not meant to work like that..  That is the whole point of vlans..  So you don't have to actually have different network wired to have a different layer 2 network.

            You use vlans so you can have different layer 2 networks run on the same wire, and have 1 switch that acts like multiple layer 2 switches in 1 box, etc.

            What exactly are you wanting to accomplish?  Do you just want specific rules for a subset of your machines?  Why can the machines not just be on 1 network, ie 10.x or 192.168.x or 172.16-31.x ?  Why do you think you need 2 layer 3 networks on the same wire?

            An intelligent man is sometimes forced to be drunk to spend time with his fools
            If you get confused: Listen to the Music Play
            Please don't Chat/PM me for help, unless mod related
            SG-4860 24.11 | Lab VMs 2.8, 24.11

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            • Q
              qshiroe
              last edited by

              IP addresses from the network 10.0.0 all reserved, and 192.168.xx network used for testing software and devices. need use two servers DHCP.

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              • Q
                qshiroe
                last edited by

                Also, conventional switches are used in networks that are not controlled, they can not create a VLAN

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                • johnpozJ
                  johnpoz LAYER 8 Global Moderator
                  last edited by

                  Agreed dumb switches are used all the time, with 1 layer 2 network and 1 layer 3 network.  Attempting to run multiple layer 3 networks over the same layer 2 is borked!

                  An intelligent man is sometimes forced to be drunk to spend time with his fools
                  If you get confused: Listen to the Music Play
                  Please don't Chat/PM me for help, unless mod related
                  SG-4860 24.11 | Lab VMs 2.8, 24.11

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                  • Q
                    qshiroe
                    last edited by

                    I realized, I will buy a manageable switches and configure vlan, thanks for reply

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                    • JKnottJ
                      JKnott
                      last edited by

                      Also, conventional switches are used in networks that are not controlled, they can not create a VLAN

                      But they should be able to pass VLANs.

                      PfSense running on Qotom mini PC
                      i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
                      UniFi AC-Lite access point

                      I haven't lost my mind. It's around here...somewhere...

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                      • JKnottJ
                        JKnott
                        last edited by

                        IPFW operates with the 2 layer, is not it so?

                        No, it works at layer 3 (IP).  In fact, some here, myself included, have complained that it doesn't filter on MAC addresses, unlike some other firewalls.

                        They hand out addresses from different subnet, the problems only when it 1 server DHCPNAK response, client linux system does not receive an address from the second server.

                        The DHCP client doesn't know to try another server, if NAKed by one.  All it does is broadcast the request and accept from the first server to reply.

                        Agreed dumb switches are used all the time, with 1 layer 2 network and 1 layer 3 network.  Attempting to run multiple layer 3 networks over the same layer 2 is borked!

                        Actually, it works OK with IPv4 and is to be expected with IPv6.  Just don't expect DHCP to sort things out, unless the server is configured to do so, matching MAC addresses to IP addresses..  Also, you can easily use static configuration for those IPv4 devices that you want to use another address block.  With IPv6, router advertisements help sort things out, with a device getting addresses on each advertised address range.  For example, you could have both global and unique local addresses on the same interface.

                        PfSense running on Qotom mini PC
                        i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
                        UniFi AC-Lite access point

                        I haven't lost my mind. It's around here...somewhere...

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                        • DerelictD
                          Derelict LAYER 8 Netgate
                          last edited by

                          Actually, ipfw can filter on MAC addresses. You might be thinking of pf.

                          Chattanooga, Tennessee, USA
                          A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                          DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
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                          • JKnottJ
                            JKnott
                            last edited by

                            ^^^^
                            My mistake.  I was thinking of pfSense, which does not have an obvious way to filter on MACs, as can be done with iptables on Linux or some versions of Cisco's IOS.

                            PfSense running on Qotom mini PC
                            i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
                            UniFi AC-Lite access point

                            I haven't lost my mind. It's around here...somewhere...

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